Conventionally, a crystal resonator is widely used as a piezoelectric resonator device used in electronic apparatuses and the like. For example, a surface-mounted crystal resonator typically has a structure in which a crystal resonator plate is bonded via a conductive adhesive or the like to the interior portion (an inner bottom face of a recess portion) of a open-topped container member (package member) having a recess portion, and the opening portion of the container member is hermetically sealed with a plate-like cover. Here, the package of the crystal resonator is configured from a container member and a lid. Container members can be obtained, for example, by laminating and firing ceramic sheets to integrally form a plurality of container members, and separating the plurality of container members by cutting the sheets along predetermined lines.
An external terminal is formed on a bottom face of the container member, and the external terminal is connected via solder or the like to a substrate inside an electronic apparatus or the like. When such an electronic apparatus or the like is used, for example, as an in-vehicle apparatus, it may receive various types of vibrations and shocks or may be used under a high-temperature environment, and, thus, a high bond strength is required in bonding of the crystal resonator and the substrate. Thus, as a conventional method for improving the bond strength, there is a method in which a side-face conductor extended in the depth direction of the container member and connected to the external terminal is formed in a castellation on a side face of the container member, and solder is applied also to this conductor portion (see Patent Document 1 and Patent Document 2, for example).
If the container member is made of ceramic, the side-face conductor is formed as follows. First, in a state where container member are still ceramic sheets, a through hole centered about an intersecting point of boundary lines between the container members (regions in which the container members are to be formed) that are vertically and horizontally adjacent to each other is formed at the intersecting point. Then, a conductor is attached to a portion around the through hole and an inner wall face of the through hole by screen printing or plating process. After the ceramic sheets are laminated and fired, the ceramic sheets are vertically and horizontally cut along lines passing through the center of the through hole. Accordingly, a container member in which the side-face conductor is formed can be obtained. However, when forming a side-face conductor at a given position on a side face of the container member, it is necessary to increase the number of ceramic sheets laminated. In this case, the total height of the container member is increased. Furthermore, in the case of ceramic sheets, after the firing, the ceramic sheets may be contracted to cause slight displacement between laminated layers. The influence of this displacement between laminated layers reaches a measurable level when the size of a crystal resonator becomes extremely small. That is to say, displacement between laminated layers makes it difficult to form a side-face conductor having a desired shape. Accordingly, the above-described bond strength improving effect obtained by forming a side-face conductor is reduced.
As a method for solving the above-described problem of displacement between laminated layers, there is a method in which the container member is made of a material such as glass or crystal. However, it is difficult to form a side-face conductor on a side face of a container member made of such a material. The present applicant searched for prior publications having this sort of configuration, but found no publication having the same configuration at the time of filing.